Power loom with a device for cutting off a woof thread

ABSTRACT

A weaving machine, in particular an airjet loom, which is fitted with a system ( 16 ) for cutting a filling thread ( 12 ′), which is being held ready for filling insertion, from a filling ( 12 ) already beaten into a fabric ( 10 ), wherein said system ( 16 ) includes a laser.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. patentapplication Ser. No. 10/069,121 filed on Mar. 1, 2002.

BACKGROUND

[0002] A. Field

[0003] The invention relates to a weaving machine with a system forcutting a filling thread that is held ready for filling insertion from afilling thread already beaten into a woven fabric.

[0004] B. Related Art

[0005] When weaving, a filling thread inserted into a shed is beaten bya reed against the fabric edge, the so-called fell line. Before thefilling thread is inserted into the next shed, it is cut off on theinsertion side of the shed. The filling thread awaiting insertion shouldbe cut at a precisely defined time in order to control the length of thenext inserted filling and/or the thread tension and to satisfy otherconditions.

[0006] In a known weaving machine of the above described kind (Europeanpatent document 0 284 766 A1), the filling thread is cut by a mechanicalcutter which contains a drive that is separate from the main machinedrive and that in turn is controlled by a programmable control system.

SUMMARY OF THE INVENTION

[0007] The objective of the invention is to design the system of theabove kind so that even more precise timing of the cutting can beachieved.

[0008] This problem is solved by using a laser as the cutting device.

[0009] The invention offers the advantage that such a laser can beactuated very rapidly and that as a result the cutting of the fillingcan be carried out in a fraction of a second. Moreover such a laseroperates without mechanical components that are subject to wear, andconsequently a predetermined precise cutting time can be maintainedwithout effect of any wear. The design of the invention provides thefurther following advantage when the filling is made of a syntheticmaterial, for instance a filament thread or one containing syntheticcomponents. Such synthetic material will be slightly fused when cut sothat the fibers of the filament threads of the cut ends are bonded toone another. This feature is especial advantageous in airjet looms. Inairjet looms there is a danger that the filling that is kept ready in amain blowing nozzle may fray in the vicinity of its end or may unravel.If this occurs, problems will arise during the subsequent fillinginsertion because of the increased danger of catching of the fibers onthe teeth of the reed. Also, the appearance of fabric edge opposite theinsertion side would then be degraded. Therefore the invention providesan advantage with respect to airjet looms. As regards other machinery,for instance gripper looms, the invention also offers substantialadvantages, in particular with regard to the accurate determination ofthe time of cutting.

[0010] Cutting systems in the form of lasers are basically known in thetextile industry, for instance from the Italian patent 1,140,124, theDutch patent 175,326 and the Japanese patent document 5 247 835 A. Inthe state of the art, however cutting systems in the form of lasers areused for fabric-severing or for loop-cutting by the forming of feltcloth.

[0011] In a further embodiment of the invention, the cutting laser shallbe fitted with an optical system that converts an emitted laser beaminto a flat beam.

[0012] In order that a low-energy laser shall suffice, its beam normallymust be focused onto a comparatively small spot. As regards threads,such a requirement may entail problems because of the practicaldifficulty of precisely aligning a filling thread to be cut with thefocus of the laser. This difficulty is circumvented by transforming thelaser beam into a flat beam. The flat beam may be positioned so that itswidth direction shall run transversely to that of the thread, andaccordingly positioning the thread and/or the laser will not raiseproblems.

DESCRIPTION OF DRAWINGS

[0013] Further features and advantages of the invention will be evidentfrom the description below and from the illustrative embodiment shown inthe drawing.

[0014]FIG. 1 is a schematic view of an airjet loom fitted with a cuttingsystem of the invention, and

[0015]FIG. 2 shows a laser with an optical system converting a laserbeam into a flat beam.

DETAILED DESCRIPTION

[0016] A fabric 10 is woven from warp threads 11 and filling threads 12on a weaving machine shown in very schematic form in FIG. 1. In a mannernot shown in detail, the warp threads 11 are periodically raised andlowered by shed-forming elements in order to form sheds into which thefillings 12 may be inserted. Following insertion, the filling thread 12is beaten by a reed 13 against the fabric edge or fell line. The reed 13is mounted on a batten profile 14 of the batten beam that pivotsto-and-fro. In the embodiment as shown, a main blowing nozzle 15 ismounted on the batten beam profile 14 that accompanies the to-and-fropivoting motion of the reed 13. The main blowing nozzle is shown in muchsimplified form. In practice, preferably two consecutively mounted mainblowing nozzles will be used. Relay nozzles are mounted in a distributedmanner in a transverse direction across the reed 13 and these relaynozzles are supplied with compressed air to help transport the fillingthreads within the shed to the opposite side.

[0017] By means of a cutting system 16, the inserted filling thread 12beaten against the fell line is cut from the filling thread segment 12′remaining within the main blowing nozzle 15. Thereupon the reed 13 andthe main blowing nozzle 15 together with the filling 12′ will pivotbackward. As soon as a new shed has been opened, a new filling insertiontakes place, and this time the filling thread 12′ will be inserted. Asalready stated above, the weaving machine is shown in a very simplifiedmanner. In practice several main blowing nozzles 15 are normally used inan adjoining and superposed manner in order to insert several fillingthreads of different types and/or colors. A number of main blowingnozzles may be used even when only identical fillings are inserted, forexample to increase the operational rate.

[0018] The end of the filling 12′ currently being kept ready is situatedwithin a moving air stream. The purpose of this air stream is to supportthe ready filling 12′ in such a way that it cannot recoil back out ofthe main nozzle 15. While this air stream holding the filling 12′ isweaker than that used to insert it, this weaker air stream neverthelessmay tend to unravel the end of the ready filling 12′, especially ifthere should be a weaving pause. This phenomenon is especially troublingwhen the filling threads are filament threads having no or little twist.Such filament threads for example, consist of a plurality of thinindividual filaments extending parallel against each other and beingfused together at distinct, spaced locations. Such a filament thread mayunravel in the vicinity of its end and thus there is a danger that whenit is inserted into the shed, it will snag on the reed's teeth. Also,this phenomenon produces an unattractive appearance of the woven fabricat the side of the cloth opposite the insertion side.

[0019] To circumvent the above drawbacks, the cutting system 16 isprovided with a pulsed laser cutting system. This laser, which ispulsed, may be a solid-state laser or preferably a gas laser and it cutsthe filling in a very short time. During cutting, a comparatively largeheat is dissipated and melts synthetic threads or synthetic components,whereby the ends of the fibers or filaments may be fused together. Eventhough the blowing air which continues being expelled from the main blownozzle 15 causes rapid cooling, the intense heat generated by the laserwill nevertheless induce melting. Accordingly the end of the readyfilling thread 12′ shall remain united.

[0020] Moreover, the laser cutting system has the advantage of rapidresponse time and very quick cutting of the filling thread. As a result,the cutting procedure can be timed very accurately in relation tooperating requirements. This feature also is advantageous when appliedto other types of weaving machines, for instance, gripper looms. Asregards gripper looms, an inserted filling thread may be severed from aready filling thread only after it has been seized and carried along bythe gripper for further insertion. It is important in this respect thatthe time of cutting be very precisely matched to that time at which thefilling thread is clamped onto and carried along by the gripper for itsinsertion.

[0021] The laser cutting beam is tightly focused in order to minimizelaser power consumption as much as possible. Illustratively suchminimization can be implemented using an optical system includingspherical focusing lens elements. On the other hand, point-focusingcreates a problem in positioning the laser because the filling threadhas a relatively small diameter. Accordingly, an optical system 17 ofspecial lens elements may be used, for example a cylindrical lense. Suchoptical system 17 converts the laser beam into a flat beam 18. The flatbeam 18 is oriented in such a way that its length direction runstransversely to the longitudinal axis of the filling thread 12, 12′ tobe cut.

[0022] The laser system 16 offers still another advantage in that thedistance between the main blowing nozzle 15 and the reed 13 may be keptcomparatively small because the laser cutting beam virtually requires nospace. Still another advantage of the system 16 of the invention is thelack of moving parts that are susceptible to wear, and as a resultlasting and accurate operation is assured.

1. A weaving machine comprising: a main weft thread blowing nozzle; areed for beating up weft threads inserted into a shed of the weavingmachine; a laser arranged to emit a laser cutting beam directed to anarea where a beat up weft thread is located adjacent an outlet of theblowing nozzle between the main blowing nozzle and the reed.
 2. Aweaving machine as claimed in claim 1, wherein said laser cutting beamis configured as a flat beam.
 3. The weaving machine as claimed in claim2, wherein said flat beam is oriented so that it extends transversely ofthe longitudinal axis of a beat up weft thread.
 4. The weaving machineas claimed in claim 1, wherein said weft threads comprise syntheticfilaments, whereby cut ends of the synthetic filaments are melted by thelaser cutting beam during cutting of the threads.
 5. A weaving machinecomprising a system adapted to cut a filling thread which is kept readyfor filling insertion from a filling thread already beaten into afabric, said cutting system comprising a laser and wherein said fillerthread comprises synthetic filaments that are caused to melt at the endsthereof and to at least partially fuse together during cutting of thefilling thread by the laser.